Apparatus for determining fuse setting data



E. WHITE ETAL 2,442,792

APPARATUS FOR DETERMINING FUSE SETTING DATA Filed Oct. 11, 1944 2 Sheets-Sheet. 1

DEAD TIME TARGET VELOCITY INVENTORS G. E. WHITE ETAL APPARATUS FOR DETERMINING FUSE SETTING DATA June 8, 1948.

2 She'gts-Sheet 2 Filed 001:. 11, 1944 ZQCLUWQQQQ FORM Umjk *lq Q9 20C om M10. 0 Loam whim EQ T 3 5 w E mm wm mww INVENTORS Gil-FORD E. WH/TE DAV/D J. CAMPBELL 4/?7'l/l/R/l. H/H/SER 7'f/0M A. 6R ENE Patented June 8, 1948 s'rAr ES mum @QF'FJTGE APPARATUSFOR DETERMINING. FUSE V SETTING DAT'A -"GifordE.-White,-' Hempstead, David J. Campbell, Richmond Hill, Arthur A.'*Hauser,Garden-'Gity, and Thom R. Greene,Hempstead,N. Y.,as signers to The-Sperry Goizporationpa corpora- -tion of Delaware Application October 11, 1944;"Serial -No; '558;2-14

12 Claims. .1 This, invention relates-toe,- fuze dead timeprediction circuit for: gun directors.

An olcvieetofthe .invention is to provide a sim- ;--p1ifie"d: iuze dead time computing .device which twilkgivez acmoreaccurate solution than existing dicate the fuze dead time-period between the set- 1 tingottheiuze and-the firing of the shot. The t-wo ,prediotions, correspondto two future 'positions .on. the path of :the target and hence an hexactsolution to this problem is to constructthe r. equivalent of two directors, which procedure,

hewevenis toocomplex to merit serious'consideration. .Thealternative is to-constru'ct a tuze prediction circuit-which .utilizes 'measures which are. correct atrtime t-inorder to anticipate or generate. a fuse. setting -fortime t+td.

1 In knowndirectorssuchas the M'7 and T20, lfuze= rateis. obtained and-multiplied by dead time .L to obtain prediction. This solutionis almost adequate, buththe residual-systematic errors are still llargeenough ,tocause. a search for a-better aplproximaticn. These directors, now .used'by. the .armed.forces,- are.we11- known to artillery oflicers and. are described .in-various manuals published cby'tthefWar' Department. The M7 director is described in Technical Manua1 .Nc.' 9-2658 .pub-

lished byi-the' War-Department. The T20 iside- 'scribed'inmanual No. 14-80853 published by the :Sperr'y' Gyroscope Company, Inc., which is available .to authorized persons.

' .lCertain directors, have a shaft actuated accordili to-fuzeftime' (Ft). 'The mechanism for actuating'ithisshaft is not a. part of the present in- .ventionand therefore is not shown .in detail. In the case of the M-'7.dire'otor,ithe shaft .is'displaced by" a lift pinwhi'ch cooperates with a" fuze foam displaced in rotation according to future rangeand translated accordingto future altitude. The cam is constructed sothat the lift imparted thereby to the lift pin' is proportional to the fuze time required for all' p'oints governed by the two factors by which the camis -displaced. iI-Iowever,- the iuze ofithe" proj ectile must be.set1before it is inserted :intmthe bre'achof the :gum andi'the operation- Of- SEttingLIthei fuze.iandz-.-loadings.may

take two to -tour-seconds' fonmanualiloadingand .aroundone second or less fonautomaticramming. This time untervalnb'etween setting; the tuze. and firing .the gunz-i-srknown'.as fuzeideadirtime' (ta) If :no correctioniw'erer mad'eufor; the fuzeudead time, the: tuze awouldl'zbe' set according to the 'fuze time (Ft): that .wasacorreot, sayaaboutitwoz, seconds before the proj ectile' wasifired; and'icouldamount to a difference :in shelhburstrposition;.andtltarget position up to three hundredvyards. 1T0 :prevent this error, .a. correctionsor .aizpredictiom .(AF) is i computed by theopresent' invention and added :to

m) 1n COl'lllfiEtiOIli withithesdescriptioniof :the invention; .the specification-milk refer atora :quanti-ty (Fm-whioh'is' a lagging measureof fuzekrate computed by a rate measuring mechanism. 'The -outpu-t or this mechanism hasan: inherent la with'respect'toinstantaneous time time In) and therefore is -referred-: to as a lagging measure of ime rate -'('F1.)

The invention -:-will-' -nowhe desoribe'd with the aid of the accompanying drawings of which -=Figs. '1" an'd 2 showschematicallytwo different embodiments of-theinvention and Fig; 3 showsa-di'al arrangement used with the second embodimentof the invention.

-A'-first embodiment ofthe invention isa rather simple mechanism-which is-shown in Fig. l-where fuze cam l0 -is'a.--par t of a;=cam assembly-cradli- 10 is *laid: out seas-to displace its lift pin! I in accordance-withruzetime=Fa "In the-present *invenitionfliftpiir H turns shaft I2 connected-wi'tl'r'andnput Of'1difi6l6l1fi31'il3. output shaft l'4;"through amack andjpinion'ar- ,rangement l5 controls the displacement of the ball carriage I 6. of. av variablespeedfldrive having l8 which. .drivesshaft .l 9:.connected to 2.3, .second input-of differential J3. .This arrangement is well a disclldrilxen at constant speedanda rcylinder vv.known. vInitial...displacement of. shaft l2. effects a :displacement .of shaft Mwandsball. carriage. I6

. some:pcsition of thecballcarriage-will balance that of shaft-I Land in. this-zposition ofequilibrium; the displacementet thew-ball carriage and :shaft 14' is :a. lagging measuremf fuzerate (-Fi.)

3 since the positioning of shaft [4 will always lag somewhat any change in position of cam pin l l Shaft l4 turns long pinion 2i meshing with gear 22 on cam 23. The cam is moved in translation in accordance with fuze dead time ta by fuze dead time knob 25. The cam actuates a lift pin 25 which displaces one input of a differential 2G by means of a rack 21 and a gear 28.

The second input of differential 28 is displaced according to Ft by shaft 29 which is driven from shaft IZbygears 30 and3l. V

These displacements are added in the difierential 25 whose output shaft 32 furnishes th data for the operation of a fuze setter or fuze transmitter indicated diagrammatically by the box 33.

The lagging measure of fuze rate (FL), represented by the displacement of shaft [4 is slightly in error due to neglect of terms of higher order than the rate term in a fuze curve. The cam 23 is laid out empirically to approximately compensate for such errors and at the same time to multiply its input displacements, thus making the fuze prediction more nearly correct than in the former rate multiplied by time method.

The method of laying out a cam such as cam 23 is well known to those skilled in ballistics. Ballistic tables furnished by the Government, among other information, give accurate data for the position of a projectile at each unit time of flight. From this information, curves may be drawn representing the trajectory of the p oj t le as o pared with the fuze curve for a suitable range of fuze dead time values.

Generally speaking, there will be a discrepancy between the true fuze curve and a fuze curve computed on the basis of the rate of change of fuze multiplied by fuze dead time, due principally to neglect of terms higher than the rate term in the latter curve.

By similar graphic procedure, it is not difficult to lay out a cam 23 according to the present invention, actuated according to the lagging measure of fuze rate F1. in one dimension and by fuze dead time in another dimension, whose output closely follows the true fuze curve.

The solution obtained by the circuit of Fig. 2 is made more accurate than that of Fig. l by taking target speed into account. The mechanism which is shown schematically, for greater clearness, is actually so designed as to fit into existing directors toreplace the present fuze rate multiplied by time type of computer.

Any suitable means providing a lagging measure of fuze rate (FL) may be used with the invention, such as the known circuit which will now be described briefly, This circuit includes a known smoothing mechanism by which spurious perturbations on the input shaft, usually due to inaccurate tracking, are smoothed out.

As in the previous embodiment, fuze cam In of the director displaces lift pin I I which actuates shaft i2 in accordance with fuze time Ft. Shaft i2 is coupled by slip'clutch M to an input 42 of a smoother differential 43. Output shaft 44 of differential 43'is coupled by gear 45 and rack. 46 to ball carriage 41 of a smoother variable speed drive 48. The disc 49' of the variable speed drive is driven'at constant speed and cylinder 50 is driven thereby. Cylinder 50 turns an input shaft 5! of an equating differential 52 having an output' shaft 53 coupled by slip clutch 54 to shaft 55 carrying gear 56 which displaces through suitable gearing a rack 51 connected to ball carriage 58 of a rate measuring variable speed drive 59. This variable speed drive is provided with a disc 60 driven at constant speed and a cylinder 6!. The latter is connected to an input shaft 62 of differential 43 and also to an input shaft 40 of differential 52. The output :member of the assembly of mechanism just described is a shaft 63 connected to shaft 55 by bevel gears 64. The displacement of shaft 63 is controlled by the position of ball carriage 58 and represents a lagging measure of fuze rate (FL). Because of the delays in the mechanical circuits just described, the generated measure of fuze rate will be lagging the exact rate. The ball carriage 58 of the rate measuring'variable speed drive 53 will be displaced in such a direction as to tend to make the rate of the rate measuring variable speed cylinder 5! equal to the rate of the smoothing variable speed drive cylinder 59. Under these conditions, the displacement of output shaft 53 of the differential which displaces ball carriage 58 represents a lagging measure of fuze rate, FL.

Generally speaking, the smoothing mechanism is used to average out errors in fuze time Ft due primarily to faulty tracking. The output of smoother differential 43 effects corresponding changes in the rate of the smoother variable speed drive 43. This variable speed drive is designed so that a change in the output of differential 43 will cause a relatively slow change in the rate of its cylinder 50. This is accomplished by choosing suitable gear ratios in all gear trains and also by selecting the proper disc speeds of the variable speed drives. Thus, if the input rate is subject to occasional brief perturbations, such perturbations will have little effect on the smoother cylinder rate before the input rate has returned to its true value. By judiciously selecting all gear ratios and disc speeds, the smoothing circuit can be designed to effect a relatively smooth measure of fuze rate, F1...

The fuze dead time circuit of the second embodiment of the invention effects total fuze dead time prediction AF by differentially adding two components of prediction (AF)1 and (AF) 2. The first of these quantities is a quantity dependent upon fuze dead time, ta and target velocity (VT) only. An angular displacement proportional to (AF)1 is introduced by positioning the index 10 of the (AF) 1 dial 1 I, Fig. 3, according to fuze dead time, ts, and an estimate of target velocity (VT).

Dial H is so laid out that when index 10 is positioned according to the appropriate values of target velocity and dead time engraved on the dial, shaft 12 on which the index is mounted will be displaced in proportion to (AF) 1. Shaft 12 is connected to one input of adding differential 13.

A preferred form of dial andindeX is shown in Fig. 3. The index 70 is marked on a transparent arm 15 attached to knob 16 which is mounted on shaft 12. The (AF)1 dial H is preferably laid out as shown in the drawing with a number of spaced curved lines approximately concentrically disposed with respect to the center of rotation of the index arm representing respectively different target velocities in miles per hour. These lines are intersected by others calibrated according to fuze dead time in fractions of seconds. The layout of the dial is empirical and is based on a study of ballistic curves for the particular ammunition used, to give at each intersection of the curves the displacement of shaft 72 proportional to (AF)1 required for the particular operating conditions.-

The second component'of fuze-dead time prediction (AFM is a quantity which is dependent upon the generated measure of the time rate of change of fuze FL, and the quantity td plus A(AF)1, where A is an empirical constant. An angular displacement proportional to (AFM is effected by the (AF)2 three dimension cam I8.

Cam I8 is rotated in proportion to FL, the output lagging measure of fuze rate, by means of a long pinion 19 on shaft 63 which meshes with ear 80 formed at one end of the cam.

The cam is translated proportionately to [td+A(AF)1l by means of a gear 8| which meshes with a rack attached to the cam. Gear BI is driven by output shaft 03 of differential 84. One input to this differential is a shaft 82 connected by gears 86 to shaft 72. Gears 86 multiply the displacement of shaft 12 by an empirical constant A whereby this input to differential 84 is A(AF) 1. The other input to differential 84 is a shaft 85 displaced in proportion to fuze dead time. A ta knob 90 is mounted on shaft 85 which is connected by gears Ill, 92 and shaft 93 to to dial 94 which cooperates with stationary index 95. Displacement of shaft 85 takes place when knob 90 is moved to position the appropriate fuze dead time value on dial 94 opposite index 95.

When cam 18 is displaced in rotation and translation as described, the lift of its lift pin 91 represents (AF)2. A rack on the lift pin meshes with gear 98 which turns shaft 99 connected to an input of adding differential 13. The displacement of output shaft I of differential I3 is proportional to total prediction AF, or AF: (AF)1+ (AF) 2.

'Shaft I02 is an input for a fuze spot correction differential IUI having a second input I02 operated by fuze spot knob I03. Output shaft I04 of the differential whose displacement is equal to AF plus fuze spot correction is connected to an input of differential I05 which adds the displacement of shaft I04 with that of shaft I06 which is proportional to fuze time Ft. Shaft I06 is connected by gears I01 to shaft I2. The output shaft I08 of differential I05 operates fuze dial I09 and a fuze transmitter, indicated by the box IIO, which usually is used to operate an automatic fuze setting device at the gun location.

Cam I8 is laid out empirically in accordance with a suitable function of F1. so that the lift pin will be displaced in accordance with the product of the function and [t11+A(AF) 1]. For example, the cam may be constructed according to the following equation:

As already pointed out, A is an empirical constant, and the functions (AF)1 and (AF)z may also be expressed by empirical equations. The optimum value of A and the mathematical expressions which are used to represent (AF)1 and (AF)2 are dependent upon (1) the sensitivity conconstant (or constants) of the differentiating circuit, and (2) the ballistics of the ammunition. These empirical expressions can .be determined by studying ballistic tables for the particular problem to give accurate corrections for targets which are flying straight line constant velocity courses.

The solution just described requires but two initial settings, one of which is a setting of dead time and a second setting which refines fuze dead time prediction according to an estimate of target velocity. After these settings have been made, the device will generate a relatively smooth '6 measure of fuze dead time prediction more accurately than former devices and with a comparatively simple mechanism.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not inalimiting sense.

What is claimed is:

1. In a fuze dead time prediction circuit, a shaft displaced according to fuze time, a. rate measuring means controlled by said shaft for obtaining a measure of fuze rate, a three dimension cam displaced in one dimension'by the rate measuring means in accordance with fuze rate, means for displacing the cam in a second dimension according to fuze dead time, a lift pin for the cam, the cam being so laid out as to displace the lift pin in proportion to the product of a function of fuze rate and fuze dead time which represents a corrected prediction value, differential means having input members controlled by said shaft and said lift pin and having an output member displaced inproportion to the sum of the displacements of theinput members, and a fuze transmitter controlled by the output member. I

2. In a fuze dead time prediction circuit, means for deriving a first prediction component which is dependent on fuze dead time and target velocity, means for obtaining a second.component of prediction comprising a three dimension cam, means for positioning the cam in one dimension according to fuze rate, means for positioning the cam in another dimension in accordance to fuze dead time and the first prediction component, a lift pin for the cam, the cam being so laid out as to displace the lift pin in proportion to a second prediction component, and means for producing a measure of totalfuze dead time prediction which comprises a diiferential having one input controlled by the first mentioned means in proportion to the first prediction component and the other input controlled by the lift pin in proportion to the displacement thereof, and an output member for the differential, the displacement of which is proportional to total fuze dead time prediction.

3. In a fuze dead time prediction circuit, means providing a measure of fuze time, a. shaft displaced thereby, a rate measuring device controlled by the shaft for obtaining a measure of fuze rate, a three dimension cam, a lift pin there for, means controlled by the rate measuring device for displacing the cam in one dimension, a differential mechanism provided with a pair of inputs having an output shaft mechanically coupled with the cam for displacing the same in another dimension, means for operating one input of the differential mechanism in accordance with fuze dead time, means for operating the other input of the differential mechanism in accordance with target velocity and fuze dead time, the cam being laid out to displace the lift pin in proportion to the product of a function of fuze rate and fuze dead time which product represents a corrected prediction value, and fuze data transmission means jointly controlled by the first mentioned shaft and the lift pin in accordance with the sum of their displacements.

4. In a fuze dead time prediction circuit, means providing a measure of fuze time, a shaft displaced thereby a rate measuring device econ.- trolled-l by? the shaft lfor obtaining a. -measure1-of fuze rate, a three dimension .cam, a lift pintherefor; means controlled by the rate measuring'device for displacing the cam in one dimensioma differential mechanism provided .Withia pair of input members, respective means for lactuating the members manually in accordance: with fuze dead time, and fuzc dead time and target velocity, an output member for the-differential mechanism coupled with the camfor displacing the same in a second dimension, the cam being laid out to displace the lift 'pin in accordance with the product of predetermined.functions of fuze dead time and fuze rate which product represents a correctedprediction value, and iuze data transmission means" jointly .controlledby the first-mentioned shaft and the lift pinin ac,- cordancewith the sum eta-their respective ,displacements.

5. Ina fuze dead timeprediction circuit, means providing a measure of fuze time, a shaft displaced thereby, a rate measuring device controlled by-the shaft 'for providing a measureof fuze rate, a three dimension cam, a lift pin-therefor,-means controlled by the rate measuring 'device for-displacing the cam-about its axis, a differential mechanism having a pairof input members and an output member coupled with the cam for displacing the same in translation, manual means for displacing a first of the inputs in accordance with'fuze dead time, other manual meansfor actuating the second of the inputs in accordance with target volecity and fuze dead time, the cam: being laid out to displace the lift pin in accordance with the product of predetermined functions of-fuze dead time and fuse rate which represents a corrected prediction value, adding differential means jointly controlled by the'first mentioned-shaft and the lift pin, and means for transmitting fuze data controlled by the output of the last mentioned differential means.

6. I In a fuze dead time prediction circuit, means providing a measure of fuze time, a shaft displacedthereby, a rate measuring device controlled by the shaft for providing a measure of fuze rate, a three dimension cam, a lift pin therefor, means controlled by the rate measuring device for displacing-the cam on its axis, a pair of 'manually operable knobs respectively provided with coopcrating dials and -shaft,-a differential mechanism operable 'bythe shaft of a first of the knobs according -to a predetermined function of fuze dead-time, a mechanical connection between "the shaft of thesecond of the knobs and the differential mechanism for operating the differential mechanism in accordance with a predetermined function of fuzedead time and target velocity; an output number for the differential mechanism operatively connected withthe Cam for displacing thesamein translation, the cam being laid out'to displace the lift pin in accordance with the product of predetermined functions of fuze dead time and fuze rate which represents a prediction value,addin g differential means jointly controlled by the first mentioned shaft,'the shaft of-the second knob of the pair and the lift pin, and meansfor transmitting fuze data controlled by theoutput of the last-mentioned differential means; I

' '7. 'I n a fuze dead time prediction circuit, means providing a-measureof fuze time, ashaft displaced thereby, a rate measuring device controlled'by-t-he shaft for providing ameasure of fuze rate, *athree dimension cam, a :lift pin there.- for, means controlled. b the vrate measuring device for displacing .the .cam onlits axis, a pairof shafts, a differentialmechanismhaving one input actuated by atfirst-rshaft of the pair, a second input for the differential, meansincluding multiplying gearing for ac-tuatingthe latter input from the second shaft of the pair, manualmeans for actuating-the firstshaft of the pair in accordance with fuzedead time, a knobhaving 3.0001)? crating scale for actuating the secondshaft in accordance "with target velocity andt fuze dead time, anoutput member for the differential mechanismoperatively connected with the cam fordisplacing thesameintranslation, the cam being laid out to displace the lift pin in accordance with the product of predetermined functions of fuze dead time andfuze rate-which represents a prediction value, ,addingdifferential means jointlycontrolledby thefirst mentioned shaft, the shaft of the secondknobof-the pair and the lift pin, and ,means for transmitting fuze data controlled by the..output of the last mentioned differential means. I

8. Ina fuze deadtime prediction circuitnneans providing a measure of fuze time, a shaft displaced thereby, a rate .measuring device-controlled byethe shaft for providing a measure of fuze rate, a three dimension cam, a lift pin therefor, means controlled bythe rate measuring device for displacing the .cam about itsaxis, a pair of manually controlled shafts, a differential mechanismhaving a'plurality of inputs, one being actuated b a first shaft of the pair in accordance with fuze dead time, means for ,displacing; the secondshaft, of the-pair in accordance with fuze dea'cttime and target velocity which represents a firstprecliction component, means including ,multiplying gear means ,operatively connecting the secondrshaft-witha second-input of thendifferential mechanism-for displacing'the same in-accorda-nce-with the'pro duct of the first prediction component and -a-- predetermined constant, an output 1 member forthe differential mechanism operatively connected with the cam for displace ingthe-same in translation thencam being ,laid out; vto displace its .lift pin. in accordance-with a second predictioncomponent, and meansforadding :the first and second components to obtain totalffuze. dead time prediction whichlcomprises a..,,differentia l mechanism. jointly controlled by the .lift pinand the secondshaft.v

9. In a fuze dead time predictionlcircuit, means providing a measure of fuze time, a shaft displaced-whereby, a ratemeasuring device controlled by the shaft for providing a measure of fuze' rate, .a three dimension cam, a lift pin thereionrneans controlle'dby-the rate measuring device fO'I G-lSPIaCiIIg-EHB- cam about its axis, a pair of {manually controlled shafts, a differential mechanism-havinga plurality ofinputs, one being actuated by-a first shaft of the-pair in accordanoewitlrfuze dead time, means for displacing the -second. shaft of -the pair-in accordance --with fuze dead time and 'target velocity which represents a first prediction-component, meansdncluding multiplying gear means operatively-connecting-the-secondshaft with a second input of the differential mechanism for di'splacingthe samein= accordance with the product of the first prediction component and a predetermined con-- stant; an-output' member fo'rthe differential mechanism operatively connected withthe cam for displacing the same in translation; the camzbe ing laid but to displaceits lift pin in accordance with a second pred-iction component, means for adding the first and second components to obtain total fuze dead time prediction which comprises a diflferential mechanism jointly controlled by the lift pin and the second shaft, means for adding total fuze dead time to fuze time comprising a differential mechanism actuated by the output of the last mentioned difierential mechanism and by the first mentioned shaft, and fuze data transmission means controlled by the output of 10 the last mentioned differential mechanism.

10. A fuse dead time prediction circuit according to claim 4 in which the rate measuring device comprises a, pair of cooperating variable speed mechanisms, one being for the purpose of smoothing the fuze time data of the first mentioned shaft and the other being for the purpose of measuring fuze rate.

11. A fuze dead time prediction circuit according to claim '7 in which the rate measuring device comprises a pair of variable speed mechanisms, one being for the purpose of smoothing the fuze time data from the first mentioned shaft and the other being jointly controlled by said shaft and the smoothing variable speed mechanism for the purpose of measuring fuze rate.

12. A fuze dead time prediction circuit accord- 10 king to claim 8 in which the rate measuring device comprises a pair of cooperating variable speed mechanisms, one for the purpose of smoothing fuze time data from the first men- 5 tioned shaft and the other for measuring the rate of change of the data.

GIFFORD E. WHITE. DAVID J. CAMPBELL. ARTHUR A. HAUSER. THOM R. GREENE.

REFERENCES CITED The following references are of record in the file of this patent:

Great Britain June 14, 1928 

